Oftentimes, plausible code is good enough, hence why people keep using AI to generate code. This is a distinction without a difference.
2 seconds to insert 100 rows in an empty database table is not "good enough" if you are doing anything that is worth doing.
No. Plausible code is syntactically-correct BS disguised as a solution, hiding a countless amount of weird semantic behaviours, invariants and edge cases. It doesn't reflect a natural and common-sense thought process that a human may follow. It's a jumble of badly-joined patterns with no integral sense of how they fit together in the larger conceptual picture.
There appears to be a similar approach in UX... plausible user experience is close enough.